Connectivity issue between a DMZ AD Virtual Machine VLAN and its gateway following a vCenter 8.0 U3 deployment

Products

• VMware vCenter Server

Issue/Introduction

• Virtual machines in a DMZ are unable to reach the default gateway.
• Users are unable to authenticate to Active Directory servers within a specific VLAN.
• Network connectivity is lost following a vCenter or ESXi upgrade.
• Physical switchport configuration does not match the virtual switch tagging method.

Environment

• VMware vSphere ESXi 
• VMware vCenter Server 

Cause

Connectivity issues occur when the physical switchport configuration (Access or Trunk) does not align with the Virtual Switch tagging mode (EST, VST, or VGT). This often results in dropped packets or unreachable gateways for specific VLANs.

Resolution

1. Verify the tagging method required for the environment.
2. If using Virtual Switch Tagging (VST), set the Port Group VLAN ID to the correct numerical ID (e.g., VLAN ####).
3. Configure the physical switchport as a trunk port and allow the required VLAN IDs.
4. If using External Switch Tagging (EST), set the Port Group VLAN ID to 0 and configure the physical switchport as an access port.
5. Check VLAN statistics on the ESXi host using the following commands:
   • esxcli network nic vlan stats set -n vmnic# -e true
   • esxcli network nic vlan stats get -n vmnic#
6. Ensure the physical network configuration (e.g., HP Aruba VLAN configuration) matches the virtual environment settings.

Additional Information

VLAN configuration on virtual switches, physical switches, and virtual machines

 

Sample configuration of virtual switch VLAN tagging (VST Mode)